/**
 * Translate the English UI text items to the user language  
 * 
 * @author Gerd Wagner
 * 
 * @param {string} txt  A UI text item to be translated.
 */
oa.trans = function( txt) {
  switch( oa.learner.language) {
    case "en": 
      return txt;
      break;
    case "de":
      return oa.trans.DE[txt] || txt;
      break;
  };
};